Remotely operated vehicles have been a high-tech but a relatively unknown piece of oil field exploration equipment. But no more.
Since the start of the Deepwater Horizon oil spill, real-time videos of ROVs often lead the national news with live feeds from 5,000 feet beneath the Gulf of Mexico (GOM). As the BP Plc.-operated well spewed oil uncontrollably, television viewers seemed mesmerized by images of the various attempts to cap the well.
At the spill site, six vessels have two ROVs each with a pair of these devices tethered to the ship around the site. The main ROV — or at least the one of which most major news organizations are getting their video — is a Hercules series vehicle from Subsea 7 controlled by Skandi Neptune, a 341-foot Norwegian vessel that was doing well completion work using its ROVs before the explosion and fire aboard Deepwater Horizon.
“This is an unusual job in that we have never had a pipeline rupture of this magnitude before, but getting video from 5,000 feet down is no big deal,” said Brett Candies, traffic and sales manager at Otto Candies LLC. “We do it all the time, but usually the general public is not interested.”
Ocean Intervention III is also on site with a pair of 150-hp ROVs. Viking Poseidon, Boa Deep C, Q4000 and drillship Discoverer Enterprise each have two ROVs. While all 12 ROVs send live video to the surface, news broadcasters typically use the feed from Skandi Neptune ROV 1, because it is focused on the oil coming from the riser.
Without ROVs, construction activity on all oil and gas wells in water deeper than 1,000 feet would be impossible, because that is the absolute limit for divers to descend.
“Deep water is the future of GOM exploration activity and this would be impossible without ROVs,” Candies said. “We would not be building our fleet of inspection, maintenance and repair (IMR) vessels, if not for the ability of ROVs to permit deepwater drilling.”
An ROV is the eyes and work device for subsea completion work. ROVs carry propulsion thrusters, lights, digital video cameras and manipulator arms to complete work otherwise done by divers.
Nick Stambolis, technical service manager for Schilling Robotics LLC, in Davis, Calif., noted the high-tech nature of ROVs. “We make an entire series of ROVs, some with titanium manipulator arms,” Stambolis said. “The on-ship operator uses a master consolette that is actually a representation of a human arm and hands. Every motion inputted into this arm is mimicked by the ROV arms.”
An ROV is controlled from a “mother” ship. The ROVs are “flown” by operators called pilots. A joystick controls the movements of an ROV, and video monitors track its progress. Devices that mimic the movement of the operator’s hands move the manipulator arms in sync on the ROV.
Typically a ship carries a pair of work ROVs, one to do the actual work and the other to provide the lighting, so operators can precisely guide the work to be done. That work can include digging trenches for pipelines, turning valves or threading pipe — literally anything divers can do in waters above 1,000 feet. Installing subsea trees and suction piles are major tasks assigned to ROVs. Their video recorders are superior to divers in inspecting pipelines and other subsea infrastructure regardless of water depth.
All ROVs have a launch-and-recovery system (LARS) to protect these delicate machines while aboard the ship and during the launch and recovery phase. Once underwater, the ROV is freed from the LARS and its thrusters take over the propulsion function. The ROVs are tethered to the ship with a bundle of cables that control all aspects of the vehicle. Once the job is complete, the ROV enters the LARS and is lifted aboard.
A typical ROV is 11.5 feet by 5 feet by 6 feet, weighs 8,500 pounds, can dive to 10,000 feet and can carry a payload of 900 pounds. It carries a quartet of 500-watt light bulbs for illumination and two manipulator arms that do most of the work. There is typically a dual control room with a duplicate set of monitors and controls for each ROV.
ROVs are also made for lighter duty projects such as treasure hunting and scientific research. It was an ROV that found Titanic.
ROVs have been totally involved in earlier attempts to cap the BP oil well. Their first job was to try to activate the blowout preventer that failed to take the signal from the control room on Skandi Neptune. The ROVs were unable to activate the shears and rams that would have cut the riser pipe closing the well.
Next they guided a cofferdam into place while a crane dropped it over the well, but this device did not work as planned. Neither did a subsequent “top hat” device. ROVs were involved in cutting the riser pipe off so a cap could be installed over the spewing oil, and that device successfully captured some of the crude.
ROVs will be involved for months in the response to the oil spil. Then they will return to the normal tasks of aiding oil production in deep water.